As mobile terminals such as smartphones and tablet computers gradually develop towards large-screen, battery capacity required by mobile terminals increasingly grows. To control a charging time not to be excessively long, high-power chargers start to be widely used.
Because a charging current of a high-power charger is relatively large, a short circuit is easily caused in a universal serial bus (USB), and in particular, in a Micro USB, and as a result, a USB or Micro USB interface is overheated and fused. Currently, a USB or Micro USB interface commonly used in a mobile terminal has a compact size, a user easily brings in a foreign matter in a usage process, and non-standard insertion and removal of a user also cause metal shell elements to rub to generate metal dust and the like, which all cause a charging short circuit in a charging process. Short circuits are distinguished by a high degree and a low degree, a short circuit of a relatively high degree may cause a relatively large current to ground, and is easily detected and avoided, but a short circuit of a slight degree causes only a relatively small current to ground, and is referred to as a micro short circuit.
To avoid a risk of a charging short circuit, currently, a charger of a mobile terminal generally has an overcurrent detection and protection function. Because a working current of a high-power charger is relatively large, a maximum current set for overcurrent detection is also relatively large. As a result, when a micro short circuit occurs in a charger, an overcurrent protection function may not be triggered. The micro short circuit cannot trigger overcurrent protection of the charger, but heat continuously generated by a small current generated by the micro short circuit can still accumulate to a relatively high temperature, and as a result, security accidents such as fusing, smoking, and fire outbreak occur on a USB or Micro USB plug or a Micro USB charging interface of a mobile terminal.
To avoid a risk of a charging micro short circuit, in another solution, a positive temperature coefficient (PTC) thermistor is built in a USB or Micro USB connector of a charging cable, and when a temperature is excessively high, a resistance value of the PTC thermistor connected to the charging cable in series increases to limit an excessively large charging current in order to avoid smoking and burning, or a negative temperature coefficient (NTC) thermistor is built in a USB or Micro USB connector of a charging cable, and when a temperature is excessively high, a resistance value of the NTC thermistor connected to the ground decreases to trigger overcurrent protection of a charger.
However, a position at which a micro short circuit usually occurs is located at an inner spring plate of an interface that protrudes at a USB or Micro USB end of a charging cable. However, the PTC thermistor or the NTC thermistor are disposed in a plastic body at the USB or Micro USB end of the charging cable, and a distance exists between the position at which the micro short circuit usually occurs and the position at which the PCT thermistor or the NTC thermistor are disposed. When a micro short circuit occurs at the spring plate, a temperature of the spring plate is relatively high, but a temperature sensed at the PTC thermistor or the NTC thermistor is insufficient and cannot trigger an impedance change of the PTC thermistor or the NTC thermistor, or only a resistance value of the PTC thermistor is enabled to increase so that charging decelerates. In this case, the micro short circuit easily causes the plastic body at the USB or Micro USB end of the charging cable to fuse or become black, which brings in a potential security risk for a user.